[fpc-pascal] Converting 32bit intel asm to Pascal or 64bit at&t asm

Thomas Schatzl tom_at_work at gmx.at
Wed Mar 9 20:18:01 CET 2011

 On Wed, 09 Mar 2011 13:23:55 -0500, Andrew Haines wrote:
> On 03/09/11 12:26, Thomas Schatzl wrote:
>> Hi,
>> On Wed, 09 Mar 2011 11:58:08 -0500, Andrew Haines wrote:
>>>       if Tmp <> Im then
>>>       begin
>>>         //Tmp := ln(Tmp)*LogBase+Shift; // same as the following 
>>> asm
>>> proc?
>>>         asm
>>>           FLD LogBase;
>>>           FLD Tmp;
>>>           FYL2X;
>> FYL2X calculates the log to the base 2 of tmp, not log to the base e 
>> of
>> tmp? Just a guess.
>> Thomas
> I originally used log2(Tmp) but switched to ln to check if it was
> correct. Thanks for noticing that, I changed it back to log2.
> The current output with the pascal code looks like it did when FLDS 
> was
> used instead of FLDL to load (%rdi). The intel code was "FLD 
> I changed this to "FLDQ (%edi)". on x32 it became FLDL and on x64 it
> became FLDS. changing the line to "FLDL (%rdi)" on x86_64 fixed the 
> last
> problem I had with the asm translation.

 Suffixes for gas for floating point are (from 

 -s 32 bit/single
 -l 64 bit/double
 -t 80 bit/extended

 With Intel syntax you can only hope that the compiler guesses 
 correctly, or add an explicit override.

 So you suggest that the assembler changes an inlined "fldq (%edi)" into 
 "flds (%edi)" on x86-64? This looks like a bug if true - it should 
 reject the "q" suffix for floating point operations.
 At least gas 2.19 on solaris x64 rejects "fldq"; actually the 2.4.2 
 release compiler transforms "fldq" into "fld" here, which gas rejects 
 too :)

 I will write a bug report.


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